Manufacturing method and steel for heavy munition casings

ABSTRACT

A manufacturing method for a heavy munition casing is provided, in which steel is rolled as a rough sheet or is forged as a slab depending on the desired casing size. Steel plates ( 2 ) produced in this way have a thickness that is somewhat greater than the manufacturing diameter of the munition casing ( 5 ). The steel used for this purpose has longitudinally oriented manganese sulfides ( 3 ), which are also shaped in the lateral direction, in addition to main shaping in the longitudinal direction, by shaping to form the shaped steel plate ( 2 ), and assume a longitudinally extending plate-shape as well. The initial material for the casing ( 5 ) is taken from an approximately rectangular steel plate ( 2 ), transversely with respect to the deformation direction. The quadrilateral piece obtained in this way is then turned to be round and is mechanically processed to form the shape of the casing ( 5 ).

The starting product for the manufacture of heavy munition casings is bar steel rolled or forged to be round. The casings are subsequently produced from this preliminary material by chip-removing manufacturing operations.

A method for increasing the strength of quenched and tempered steel and its use for the production of a search-igniter sub-munition casing is disclosed with DE 39 18 700 C2. The quenched and tempered steel here is the quenched and tempered steel 30CrNiMo8.

The conventional material for heavy munition casings is a quenched and tempered steel with largely isotropic material properties, such as in particular a 42CrMo4- or a 34CrMo4 steel that is highly quenched and tempered, for example to strength values above 1100 N/mm². The high strength is to promote a low-deformation complex fracture structure at bursting. However in practice, under conventional conditions only a tough, plastic fracture structure is formed at the bursting apart of a smooth munition casing (FIG. 1 a).

In contrast, brittle steels only cause a bursting apart into a few main fractures (FIG. 1 b). The addition of embrittling phases such as sulfur, hardened as manganese sulfide, predominantly promotes the formation of longitudinally orientated fractures, without triggering the desired complex fracture behavior.

For this reason, net-shaped predetermined fracture points are inserted through mechanical material removal (FIG. 1 c) to realize the desired brittle, multipart fracture behavior in a supplementing manner and at high cost. This manufacturing process is very laborious.

The object of the invention is to simplify this process and to disclose a steel that enables a simplification.

The object is achieved by the features of claim 1 as well as claim 4. Advantageous embodiments are shown respectively in the subordinate claims.

The present invention is based on the concept of simplifying or replacing the very laborious manufacturing process by using a suitable improved steel concept. A suitable steel material is used that combines the desired high-strength material properties for heavy munition casings with a complex, multipart burst behavior.

The use of a highly quenched and tempered steel with a transverse plate-shaped manganese sulfide phase is provided for, in particular the use of a manganese-chromium alloyed quenched and tempered steel with a transverse fiber structure.

A quenched and tempered steel of this type is realized in that the steel plate, whose thickness is somewhat greater than the manufacturing diameter of a munition casing, is rolled as a rough sheet or forged as a slab, depending on the desired casing size. The steel used for this has longitudinally orientated manganese sulfides. Through the shaping to produce a plate, the manganese sulfides in addition to the main shaping in the longitudinal direction are also deformed in the transverse direction and finally assume a longitudinally extended shape in the form of a plate. The initial material is now no longer taken from a round steel, but transverse to the deformation direction from the approximately rectangular steel plate, for example by sawing. The quadrilateral piece obtained in this manner is then turned to be round and is mechanically processed to comply with the drawing. In the wall cross section of the munition casing the plate-shaped manganese sulfides are arranged radially in high density. During the bursting, these manganese sulfides serve as natural predetermined fracture points and effect a multipart fracture behavior of the munition casing.

The munition casing produced according to this manufacturing process has the desired multipart fracture behavior during the bursting, without a further heat treatment or an additional incorporation of predetermined fracture points being required; the burst behavior of the munition casing corresponds to the desired multipart fracture structure that according to prior art could only be achieved by predetermined fracture points. Thus the insertion of predetermined fracture points can also be omitted.

The invention is to be explained in more detail based on an exemplary embodiment with drawing.

They show:

FIG. 1 a-c Fracture behavior at the bursting apart of the munition casings according to the prior art,

FIG. 1 d The fracture behavior at the bursting apart of the munition casing according to the invention,

FIG. 2 A diagrammatic representation of the position of the unworked casings in a steel plate and reference to the deformation direction of the manganese sulfides,

FIG. 3 the radial arrangement of the manganese sulfides in a munition casing upon use.

FIG. 1 a-c show the fracture behavior of conventionally produced munition casings, to which reference has already been made in the specification introduction.

FIG. 2 shows a diagrammatic representation of the position of the unworked casings or initial pieces 1 in a steel plate 2. 3 refers to the incorporated manganese sulfides.

The steel plates 2, whose thickness is somewhat greater than the manufacturing diameter of the casing 5, are rolled as a rough sheet or forged as a slab, depending on the desired casing size. The width of the steel plates 2 corresponds thereby at least to the length of a munition casing 5, preferably a multiple thereof. Through the shaping to produce a plate 2, in addition to the main shaping, the manganese sulfides 3 are deformed in the longitudinal direction and also in the transverse direction, and finally assume a longitudinally extended shape in the form of a plate. Directly after the heat shaping, the steel plate 2 is quenched and tempered for strength during use. The proposed steel thereby ensures an adequate through quenching and tempering over the entire cross section. The steel or the steel plate 2 has longitudinally orientated manganese sulfides 3 in high density. The fibers formed through manganese sulfide phases are obtained using an initially quenched and tempered, slab-shaped starting body (steel plate 2) with a high proportion of manganese sulfides, from which initial pieces 1 for the casing 5 are now taken transverse to the deformation direction through sawing or the like.

Due to the high sulfur content, the steel 2 is easily machinable in spite of high strength. The quadrilateral piece 1 removed from the steel plate 2 is sawed to be round in a further manufacturing operation and is mechanically processed to comply with the drawing, i.e. the sections are mechanically processed by turning and drilling to the dimensions.

The plate-shaped manganese sulfides 3 are arranged radially in high density in the wall cross section of the munition casing 5 (FIG. 3). The embrittling sulfides are now situated radially in the casing wall 4 and under bursting pressure in the function of the munition casing 5, trigger local fractures, i.e. during bursting the sulfides function as natural predetermined fracture points and cause a multipart fracture behavior of the munition casing 5 (FIG. 1 d).

The steel to be quenched and tempered for use is preferably produced with the following chemical composition:

0.30 to 0.60% carbon Max. 1.0% silicon Max. 2.0% manganese Max. 0.05% phosphorus 0.03 to 0.25% sulfur Max. 2.0% chromium Max. 0.5% molybdenum as well as remainder of iron and unavoidable impurities.

The following composition has shown itself to be preferred within these ranges:

0.35 to 0.45% carbon 0.30 to 0.60% silicon 1.40 to 1.60% manganese Max. 0.035% phosphorus 0.05 to 0.10% sulfur 1.80 to 2.10% chromium 0.15 to 0.25% molybdenum as well as remainder of iron and unavoidable impurities.

Comparable steels have been sold for a long time under material No. 1.2312 for plastic molds (Steel/Iron List, Verlag Stahl Eisen, Dusseldorf).

This manganese/chromium alloyed steel or the steel plate 2 is preferably quenched and tempered to the desired strength directly after the shaping, which strength is preferably in the range of 900-1200 N/mm². The through quenching and tempering of this manganese/chromium alloyed quenched and tempered steel has been proved up to approx. 400 mm plate thickness and is thus adequate for all munition sizes.

FIG. 2 Deformation direction

-   -   Position of the casing in the steel plate     -   Manganese sulfides

FIG. 3 Wall section of munition casing

-   -   Position of the manganese sulfides 

1. A manufacturing method for the production of a steel or of steel plates, wherein the method comprises the following steps: (a) rolling steel plates as a rough sheet or forging steel plates as a slab, depending on a desired size; and (b) through shaping of the rough sheet or through producing a shaped plate, wherein manganese sulfides situated in the shaped plate, in addition to the main shaping in a longitudinal direction, are also deformed in a transverse direction and assume a longitudinally extended shape so that the manganese sulfides form in a plate-shape.
 2. A manufacturing method according to claim 1, wherein the shaped plate is quenched and tempered to the desired strength preferably directly after shaping.
 3. A manufacturing method according to claim 2, wherein the desired strength is in the range of 900-1200 N/mm².
 4. Steel for use for the manufacture of a heavy munition casing according to claim 1, wherein the steel comprises: (a) 0.30 to 0.60% carbon, by weight; (b) a maximum of 1.0% silicon, by weight; (c) a maximum of 2.0% manganese, by weight: (d) a maximum of 0.05% phosphorus, by weight; (e) 0.03 to 0.25% sulfur, by weight: (f) a maximum of 2.0% chromium, by weight; (g) a maximum of 0.5% molybdenum, by weight: (h) as well as a remainder of iron and unavoidable impurities.
 5. Steel according to claim 4, comprising: (a) 0.35 to 0.45% carbon, by weight; (b) 0.30 to 0.60% silicon, by weight; (c) 1.40 to 1.60% manganese, by weight: (d) a maximum of 0.035% phosphorus, by weight; (e) 0.05 to 0.10% sulfur, by weight: (f) 1.80 to 2.10% chromium, by weight; (g) 0.15 to 0.25% molybdenum, by weight: (h) as well as a remainder of iron and unavoidable impurities.
 6. A munition casing, produced according to the manufacturing method according to claim 1, wherein the munition casing includes: (a) steel comprising i. 0.30 to 0.60% carbon, by weight; ii. a maximum of 1.0% silicon, by weight; iii. a maximum of 2.0% manganese, by weight; iv. a maximum of 0.05% phosphorus, by weight; v. 0.03 to 0.25% sulfur, by weight: vi. a maximum of 2.0% chromium, by weight; vii. a maximum of 0.5% molybdenum, by weight; viii. as well as a remainder of iron and unavoidable impurities: (b) a casing wall made by taking an initial piece from a plate made of the steel, wherein the initial piece is taken transverse to a deformation direction through sawing, and wherein the casing wall defines an interior space; and (c) plate-shaped manganese sulfides situated radially in high density in the steel in a cross section of the casing wall, wherein the manganese sulfides embrittle the steel and are arranged radially in the casing wall so that when the interior space is under a bursting pressure, local fractures are triggered in the casing wall.
 7. A munition casing according to claim 6, wherein the thickness of the plate is somewhat greater than a manufacturing diameter of the munition casing, wherein a width of the plate corresponds to at least a length of the munition casing.
 8. Steel according to claim 4, wherein the steel has a strength in the range of 900-1200 N/mm².
 9. Steel for use for the manufacture of a heavy munition casing according to claim 1, wherein the steel consists essentially of: (a) 0.35 to 0.45% carbon, by weight; (b) 0.30 to 0.60% silicon, by weight; (c) 1.40 to 1.60% manganese, by weight; (d) a maximum of 0.035% phosphorus, by weight; (e) 0.05 to 0.10% sulfur, by weight; (f) 1.80 to 2.10% chromium, by weight; (g) 0.15 to 0.25% molybdenum, by weight; (h) as well as a remainder of iron and unavoidable impurities, wherein the steel has a strength in the range of 900-1200 N/mm².
 10. Steel for use for the manufacture of a heavy munition casing according to claim 1, wherein the steel consists of: (a) 0.35 to 0.45% carbon, by weight; (b) 0.30 to 0.60% silicon, by weight; (c) 1.40 to 1.60% manganese, by weight; (d) a maximum of 0.035% phosphorus, by weight; (e) 0.05 to 0.10% sulfur, by weight; (f) 1.80 to 2.10% chromium, by weight; (g) 0.15 to 0.25% molybdenum, by weight; (h) as well as a remainder of iron and unavoidable impurities.
 11. Steel according to claim 10, wherein the steel has a strength in the range of 900-1200 N/mm².
 12. Steel according to claim 4, wherein the steel includes plate-shaped manganese sulfides.
 13. Steel according to claim 9, wherein the steel includes a phase comprising plate-shaped manganese sulfides.
 14. Steel according to claim 10, wherein the steel includes a phase comprising plate-shaped manganese sulfides formed by the manganese and the sulfur.
 15. A munition casing according to claim 6, wherein the thickness of the plate is somewhat greater than a manufacturing diameter of the munition casing, wherein a width of the plate corresponds to at least a multiple of a length of the munition casing. 